Energy from the ground

Experts at Mott
MacDonald are advocating a radical heating and cooling system that
can be built into tunnels or the foundations of new buildings to
provide efficient and sustainable air-conditioning – an approach
sparked by work at the Technical University of Vienna, a centre of
excellence in geothermal energy, and the successful application of
the technology on the Viennese metro system.

“Much of the UK’s recent R&D into alternative energy sources
has focused on wind power, with little attention to the commercial
viability of extracting energy from the ground to heat and cool
buildings, despite its many proven benefits,” explains our leading
foundations specialist Alan Powderham who, together with fellow
geotechnical expert John Perry, organised a seminar on the subject
in London.

Our proposal exploits foundations as heat absorbers, providing
heating or cooling through geothermal energy. “The technique is
based on casting high density polyethylene pipes into concrete
piles, base slabs or diaphragm walls in contact with the ground,”
explains John. “A water/glycol mixture is then circulated through
these pipes to heat buildings, bridges and underground space in
winter and cool them in summer.” Research at the Technical
University of Vienna suggests that for every watt of energy needed
to operate the system, between 3.5W and 5W is returned as heat
energy. “We’ve carried out an in-depth evaluation of potential
application for Heathrow’s Terminal 5 and other projects are also
being considered,” says Alan. “Meanwhile we’ve been strengthening
our relationships in this area with other universities besides
Vienna, including Cambridge, Imperial College and Cardiff, as well
as linking strongly with CIRIA.”

Already harnessing energy from the ground is our design for
Manchester’s new £113 million Civil Justice Centre comprising court
rooms, tribunal and hearing rooms and facilities for judges. Our
solution incorporates natural and renewable energy sources
including natural ventilation and lighting as well as groundwater
source cooling.

Groundwater provided via two boreholes will be used to cool the
building both directly, using under-floor cooling systems and heat
exchangers, and indirectly by providing heat rejection for
chillers. The scheme improves chiller efficiency by reducing normal
operating temperatures, resulting in the installation of two rather
than three 600kW chillers. Total operational energy savings
calculated against conventional cooling systems will be around
200MWh per year – a shining example of sustainable design.